IIt was noted that dielectrics comprising nano-crystalline HfO2 in gate stacks, with thin SiO2/SiON interfacial transition regions, exhibited significant asymmetries with respect to the trapping of Si substrate-injected holes and electrons. Based upon spectroscopic studies and ab initio theory, electron and hole traps in HfO2 and other transition metal elemental oxides were attributed to O-atom divacancies clustered at the internal grain boundaries of nanocrystalline films. Suggested techniques for suppressing grain boundary defects included the use of ultra-thin (<2nm) HfO2 fims, chemically phase-separated high-HfO2 content silicate films and non-crystalline Zr/Hf Si oxynitride films.

Spectroscopic Studies of O-Vacancy Defects in Transition Metal Oxides. G.Lucovsky, J.Lüning, L.B.Fleming, M.D.Ulrich, J.E.Rowe, H.Seo, S.Lee, P.Lysaght, G.Bersuker: Journal of Materials Science - Materials in Electronics, 2007, 18[1], 263-6